comet 67P/Churyumov–Gerasimenko

Europe’s Philae lander — still latched inside its mothership — has been activated and should be ready for release Wednesday to begin a daring first-ever descent to a comet, the mission’s flight director said Tuesday.

This week marks the pinnacle of the professional careers of many scientists, when the European Space Agency plans to put down a three-legged robotic lander on a comet, a risky first-of-a-kind endeavor that could rewrite textbooks on the history of the solar system.